Abstract: A mold 25 for molding semiconductor chips 23 and 24 serving as a light emitting element and a light receiving element, respectively, is made of a material capable of transmitting light. A groove 27 is formed on the region where light is emitted from and incident on the semiconductor chips so that it constitutes a reflecting face. Thus, the light is emitted and incident through the side E of the mold. In this configuration, the outer size of the light receiving element or light emitting element can be minimized, and the module provided with these semiconductor chips can also be miniaturized.

Abstract: A current to voltage conversion circuit is formed of a differential amplifier circuit (1) with a negative input terminal connected to a light receiving element (3) and a register (4) which feeds back an output signal to the negative input terminal of the differential amplifier circuit (1) thereof. The variable gain amplifier circuit (5) amplifies the output voltage of the current to voltage conversion circuit to detect the bottom value of the output signal thereof. The comparator circuit (7) compares the bottom value with the reference value Vr1 so that current flowing through the resistor (4) can be adjusted according to the difference between the bottom value and the reference value Vr1. The offset of the output signal from the variable gain amplifier circuit (5) supplied through the output terminal OUT is thereby adjusted.